Question

The number of point(s) of discontinuity of $f\left(x\right)=\left[5x\right],x\in [0,1]$ is

Answer 1

$x\in [0,\frac{1}{5})$ $\Rightarrow f\left(x\right)=0$
$x\in [\frac{1}{5},\frac{2}{5})$ $\Rightarrow f\left(x\right)=1$
$⋮⋮$
$x\in [\frac{4}{5},1)$ $\Rightarrow f\left(x\right)=4$
and at $x=1$ $\Rightarrow f\left(x\right)=5$
$\Rightarrow 5$ point of discontinuity.